<html>
<head>
<!--
/*
 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/protocol/package.html $
 * $Revision: 496070 $
 * $Date: 2007-01-14 04:18:34 -0800 (Sun, 14 Jan 2007) $
 *
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
-->
</head>
<body>
HTTP protocol execution framework.

Apart from simply sending and receiving messages, there are a lot
of things to consider when communicating with HTTP. Many details
such as transport encodings or connection management are handled
by setting up or interpreting
{@link org.apache.http.Header headers} in the messages.
In order to relieve applications from the responsibility of
implementing these nitty-gritty details of the protocol,
HTTP components provides an execution framework that sets up
some of the headers before sending a message, and interprets
headers when a message has been received.
<br/>
An HTTP {@link org.apache.http.protocol.HttpProcessor processor}
typically keeps lists of so-called interceptors that will be executed
before a message is sent and after it has been received.
An application should initialize a processor, set up the lists
with the required and desired processors, and then communicate
through that processor. There are four kinds of interceptors,
depending on whether they act on
{@link org.apache.http.HttpRequestInterceptor requests} or
{@link org.apache.http.HttpResponseInterceptor responses},
on the client or server side:

<table border="1" cellpadding="5">
<tr><th></th>
    <th>Client</th>
    <th>Server</th>
</tr>
<tr><th>Request</th>
    <td>prepares headers before a request is sent</td>
    <td>interprets headers when a request is received</td>
</tr>
<tr><th>Response</th>
    <td>interprets headers when a response is received</td>
    <td>prepares headers before a response is sent</td>
</tr>
</table>

<p>
{@link org.apache.http.protocol.HttpRequestExecutor HttpRequestExecutor}
is a processor for the client side,
{@link org.apache.http.protocol.HttpService HttpService}
for the server side.
On the client side, a {@link org.apache.http.protocol.HttpContext context}
is used to tie together a request, the response to it, and other data
that might be associated with the request execution. It is passed to
the request executor whenever needed.
</p>

<p>
<font size="+1">
<i>
Information about required and recommended interceptors for the
client side will be provided elsewhere. For the time being, please
refer to the comments in the example applications or ask on
one of the mailing lists.
</i>
</font>
</p>

<p>
<b>Note:</b>
If you want to develop a server-side application, we recommend that
you implement your application as a servlet running in a servlet engine
like <a href="http://tomcat.apache.org/">Tomcat</a> or full-blown
JSEE container like <a href="http://geronimo.apache.org/">Geronimo</a>.
If you prefer to implement a server-side application based on our
{@link org.apache.http.protocol.HttpService HttpService}, we'll
assume that you know what you're doing and that you don't need
help in figuring out which interceptors need to be configured.
</p>


</body>
</html>
